You Can Do This! The Sleep Diet Is Here

The minimum amount of sleep you need for weight loss is seven and a half hours a night, our experts say. But the closer you can get to your ideal sleep time—see #4, below, to figure that out—the better your results will be. (Sorry, but sleeping more than that won't help you drop more pounds!) And you don't have to be clinically overweight for this to work. What to do:

1. Go to sleep and wake up at the same time every day.

Write down the time you need to get up in the morning, then count back seven and a half hours. That is the time you need to be in bed. But we're not out to kill all your fun: On Friday or Saturday nights, you can go to bed one or two hours later than usual and sleep in one or two hours the next morning—as long as you get your required seven and a half hours.

2. Start a bedtime routine.

Create a presleep ritual—such as light reading, a hot bath, stretching—beginning somewhere between 45 minutes to an hour before the time you've planned to close your eyes. Pretty soon, your body will start to associate specific actions with relaxation and falling asleep. And turn off your TV, computer, BlackBerry and cell phone before that time begins. "When your brain senses light shining in your eyes, it stimulates the wake response and lowers melatonin, the hormone that cues you to feel drowsy," says Steven Park, M.D., author of Sleep, Interrupted.

3. Watch your caffeine and alcohol habits.

Don't have any caffeine after 2:30 P.M. (including caffeinated tea and soda), and avoid sipping alcohol three hours before bedtime. Booze may knock you out at first, but it keeps you from getting deep sleep, says Breus. As the sleep-inducing powers wear off, you may even wake up.

4. Experiment with exactly how much sleep you really need.

According to the National Sleep Foundation, some women require as many as nine hours of sleep a night. If you're snoozing seven and a half hours and still can't wake up without your alarm, you need more. Try hitting the sack 15 minutes earlier each night until you reach the perfect time for you—it may take a week or so before you reach your own ideal sleep number.

What Might Go Wrong (and How to Fix It)

Sleeping more sounds easy, but it can be hard. Here's how our testers conquered their biggest hurdles:

"I missed my TV! Going to bed at 9:30 meant I had to skip my favorite shows." —JohnsonTiVo them, recommends Dr. Lamm. "Even if you do have to totally give up an hour or so of TV, think in terms of what you're getting in return—a better and healthier body." Says Johnson, "To tell you the truth, once I got out of the habit of seeing those shows every week, they just became less important to my life."

"Falling asleep before 11:00 was really hard at first. It didn't seem right to go to bed so early." —Hamilton-Romeo

Breus advises that night owls like Hamilton-Romeo switch to the new time line slowly, then stick to it. "I just had to let go of the idea that I needed to do everything," says Hamilton-Romeo. "Once I actually started going to sleep earlier, I felt so amazing, I wondered why I'd never done it before!"

"I thought I couldn't survive the day without my afternoon coffee fix." —Johnson

If you're a die-hard coffee addict, cutting yourself off at 2:30 P.M. may seem cruel and unnecessary, but trust the experts here—caffeine does affect your sleep in subtle ways, even if you can't feel it. "If you're struggling in the first few weeks to give up coffee," says Breus, "try weaning yourself off slowly with a cup that's half regular and half decaf, then go all the way."

"I wondered at first how I was going to find time to spend with my husband when I had to be in bed so early and fit in a bedtime ritual.'" —Braverman

This is a biggie for any woman with a live-in partner or children, says Dr. Lamm. His recommendation: "Ask your partner to get in on the routine with you. It can be sex, it can be cuddling and reading, it can be a warm shower. If that's the only hour you guys get to spend together, chances are he'll be willing to skip an hour of TV in favor of some quality time with you." That's exactly what Braverman did. Just a few weeks into the makeover, her husband actually started doing yoga stretches with her before bed. "He loves it now!" she says.